On Fri, Nov 06, 2009 at 12:39:36PM -0600, Serge E. Hallyn wrote: > Quoting Sukadev Bhattiprolu (sukadev@xxxxxxxxxx): > ... > > + If a pid in the @pids list is non-zero, the kernel tries to assign > > + the specified pid in that namespace. If that pid is already in use > > + by another process, the system call fails (see EBUSY below). > > + > > + The order of pids in @pids is oldest in pids[0] to youngest pid > > + namespace in pids[nr_pids-1]. If the number of pids specified in the > > In the sys_choosepid() discussion, Matt suggested it would be more > user-friendly to have the pid for the youngest pidns be pids[0]. > That way the user doesn't have to know their pidns depth. As far as I could see, Suka's solution also does not require knowing the pidns depth (aka level). He made it so that copy_from_user() adjusts its destination using the discrepancy between the number of pids passed and the number of levels. If userspace passes an array with n pids and there are k namespace levels then clone_with_pids() makes sure that the kernel sees a pid array like: index 0 ... k - (n + 1) ... k - 1 +-----------------------+-------------------------+ pid_t | 0 ..................0 | <copied from userspace> | +-----------------------+-------------------------+ So even though the order is different from choosepid() the calling task still doesn't need to know its pidns level. Of course, just like choosepid(), n <= k or userspace will get EINVAL. Cheers, -Matt Helsley _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
